Bayesian Inversion of Wrapped Satellite Interferometric Phase to Estimate Fault and Volcano Surface Ground Deformation Models
Abstract
Phase unwrapping is the process of recovering the absolute phase from unambiguous wrapped phase values that are measured modulo 2pi rad. From a mathematical point of view, phase unwrapping is an inverse problem, however, it is ill-posed and notoriously difficult to solve in the presence of noise. Meanwhile, phase unwrapping errors severely impact the estimation of earthquake and volcano source parameters using interferometric observations, therefore avoiding phase unwrapping completely is desirable.
A potential solution to avoid the unwrapping error issue completely, is to carry out a geophysical inversion directly on wrapped phase observations. We propose a novel approach that we can invert directly the interferometric wrapped phase, circumventing the ill-posed phase unwrapping processing step (Jiang and González, 2020). This approach includes (1) a downsampling algorithm, (2) a method to estimate the covariance function of wrapped phase, (3) an appropriate misfit function between the observed and the simulated wrapped phase. We also assess the uncertainties of source parameters within a Bayesian approach. Finally, we demonstrate the proposed method on synthetic cases with variable noise levels and one real earthquake case. We show that the method is robust in challenging noise scenarios. We also show an improvement with the Bayesian approach in performance with respect to similar previous methods, resulting in avoiding any influence of seed starting models, and escaping local minima. For earthquakes studies, we further extend the uniform slip inversion to the distributed fault slip inversion. A physics-based crack model is incorporated as the constrain. We demonstrate the performance on synthetic cases and the results are compatible with those based on current state-of-the-art method with unwrapped phase. In conclusion, our proposed method is complementary to existing inversion methods with unwrapped phase. We expect it to be an alternative solution in earthquake and volcano cases where phase unwrapping is difficult or even impossible. Jiang, Y., & González, P. J. (2020). Bayesian inversion of wrapped satellite interferometric phase to estimate fault and volcano surface ground deformation models. Journal of Geophysical Research: Solid Earth. https://doi.org/10.1029/2019JB018313- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMG024...07J
- Keywords:
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- 1240 Satellite geodesy: results;
- GEODESY AND GRAVITY;
- 1241 Satellite geodesy: technical issues;
- GEODESY AND GRAVITY;
- 1294 Instruments and techniques;
- GEODESY AND GRAVITY;
- 1295 Integrations of techniques;
- GEODESY AND GRAVITY